Many vehicles are equipped with automatic braking systems that use friction between a rotor and a brake lining, where the brake lining is on a brake pad, or friction between a drum and a brake lining, where the brake lining is on a brake shoe. One characteristic of friction brakes is a fading of vehicle braking system performance, or brake fade. Brake fade is a reduction in stopping power that may occur after repeated or sustained application of a friction brake. Brake fade is caused by a buildup of heat in the friction material of the brakes including the brake lining, brake rotor, brake drum, or brake fluid. A loss of stopping power, or fade, may be caused by friction fade or fluid fade. Brake fade often occurs during travel down a long, steep decline. Disc brakes are more resistant to brake fade because heat can be vented away from the rotor and pads, while drums tend to hold in the heat.
Also, many vehicles are equipped with an adaptive cruise control (ACC) system. The ACC, working with conventional engine based speed control, may automatically apply vehicle friction brakes to maintain a constant speed or following distance. The ACC of a vehicle traveling down a hill or following a different vehicle may actively decelerate the vehicle by reducing the power output of the engine, or applying the vehicle brakes to maintain a speed of the vehicle or a distance between the vehicle and the other vehicle. A continual application of a friction brake, for example, during a downhill following mode may overwork the friction brakes and lead to brake fade. In order to avoid brake fade, some ACC systems are designed to disengage when the friction brakes exceed a temperature.